If you don't have a gun...

You will have assholes who drink beer in an underpass and let their dogs get off the lead. The assholes will have "terrier" dogs who attack blind people's guide dogs.
http://news.bbc.co.uk/1/hi/england/london/8368548.stm

"What made this awful incident even more harrowing was the fact that the man made no effort to assist her or to check that she was all right once the attack was over.

The man was described by police as white, in his mid to late-20s, around 5ft 11ins and of slim build. He had a cropped beard and brownish to red hair which was cut short and was wearing black tracksuit bottoms and a grey top.

There is CCTV footage at the BBC site.

Actually, I know a lot of yanks that let their dogs run loose as well so this is serious sarcasm. I should make that clear since some people are too stupid to catch that.